First, before writing a letter, you can define the scope: where to develop customers, what are the similarities, and what information you may pay attention to?
Second, try to collect information: the location of the company, the size and type of the company, and the identity and responsibilities of the recipients can all help the analysis. You want to attract points from the other side's position and add these ideas to the letter. If there is no reply, it means that the recipient's company has no intention at present or the recipient is not interested in the content of the letter. After you get this feedback, you can change customers or content.
Third, some tips: there must be multiple templates for reply; Copy to customers similar to * * *; Attach some pictures and more links to the email; The same customer should not write more than one letter a week, and the contents of the previous letters should not be the same. If you write this letter as an application for membership, you will feel good.